Most racing wheelchairs are propelled by pushrims on the outside of the two drive wheels. The rider reaches back and puts the heels of their hands on the pushrims of the two drive wheels. They then push the pushrims down as the wheels rotate.
There are several weaknesses to this design. First, this design is inefficient, having considerable lost and wasted motion. The power stroke is only approximately one fifth of a revolution requiring one's hands and arms to return to the starting position after each power stroke. During the return stroke, energy is consumed but not transmitted to the drive wheels as the hands return empty to the original position. Not only is this inefficient, but during this time the wheelchair is out of control and can be particularly dangerous when ascending or descending a ramp or other irregular terrain. Second, this type of motion can also lead to repetitive motion injuries such as carpal tunnel syndrome. Third, the rider's high position produces a high center of gravity. Fourth, the rider can only inefficiently brake by pushing their hands against the tires or pushrims.
Advanced racing wheelchairs address these weaknesses by having a small diameter push rim for higher top speed, drive wheels that tilt out at the bottom for stability and an extended front wheel for balance. They are available from such firms as Invacare and Sunrise Medical.
Many attempts have been tried to change the basic wheelchair design for use by both physically challenged and able-bodied people. They usually fall into five main groups.
The first group uses levers. This group includes:
Patent No. Inventor Title Date 4,682,784 Anderson Wheelchair with Variable Ratio Jul 28, 1987 Propulsion 4,705,284 Stout Human Powered Vehicle Nov 10, 1987
The second group has pushrims outside the two drive wheels. This group includes:
 Patent No. Inventor Title Date 5,028,064 Johnson Racing Wheelchair Jul 3, 1991 3,563,568 Sasse Variable Rotary Drive Feb 16, 1971 Mechanism for Wheel Chairs 4,727,965 Zach Geared Hub with Freewheel for Mar 1, 1988 Wheel-Chairs
The third group has small handles outside the two drive wheels. This group includes:
 Patent No. Inventor Title Date 5,037,120 Parisi Wheelchair Manual Drive Aug 6, 1991 Mechanism 4,758,013 Agrillo Hand Crank Wheelchair Drive Jul 19, 1988
The fourth group has direct drive handles inside the two drive wheels. This group includes:
 Patent No. Inventor Title Date 4,066,273 Lobar Toy Car Jan 3, 1978 4,655,470 Lin Hand-propelled Wheeled Device Apr 7, 1987 for Children
The fifth group has hand cranks in front of the rider using a chain to drive one wheel in front. This group includes:
 Patent No. Inventor Title Date 4,109,927 Harper Hand Powered and Controlled Aug 29, 1978 Tricycle
U.S. Pat. No. 4,682,784 and 4,705,284 both use dual reciprocating levers, and have several speeds. The required push/pull arm motion does not fully use the rider's muscles (only the push moves the vehicle) and the high sitting position (about 13") is unstable in turns.
U.S. Pat. No. 5,028,064 has a low, stable sitting position but still uses pushrims. Also, the rider can not easily move back and forth, thus preventing the abdominal and back muscles from helping propel the vehicle.
U.S. Pat. No. 3,563,568 and 4,727,965 have multiple speeds but also have pushrims and a high sitting position.
U.S. Pat. No. 5,037,120 has an efficient circular arm motion. However, a high sitting position, no brakes, and a rigid seat back hamper the rider's performance. In addition, the this design has no coasting feature.
U.S. Pat. No. 4,758,013 has an efficient circular arm motion, brakes and reverse. However, a high sitting position, rigid seat back, and lack of easy frame adjustment also hamper the rider's performance.
While U.S. Pat. No. 4,066,273 and 4,655,470 use the major muscle groups and have a low, stable seat, they have only one speed, cannot freewheel, and have no brakes. A similar device for children is commercially available through Lakeside Learning.
U.S. Pat. No. 4,109,927 has a front wheel that is driven by a chain connected to a hand cranked mechanism. The crank and front wheel look like the pedals and back wheel of a bicycle. This concept has an efficient circular arm motion, plurality of speeds and brakes. However, performance is hampered in this model because the rider cannot turn quickly. The front wheel is between the rider's legs and so its turning angle is limited. Also, sudden stops can cause the rider's chest to impact the chain sprocket. Similar devices are commercially available through Invacare, Sunrise Medical and Brike.
In addition, none of these patents show a seat that is comfortable for long periods. The seats are also not ventilated and provide no support for the rider as they rock back and forth. Moreover, most of these patents show a frame that cannot be adjusted for different sized riders.
It has been shown that the choices in outdoor exercise for physically challenged athletes have limitations. Furthermore, even able-bodied people have limited choices in physical exercise for the upper body. Millions of people run, bicycle, or rollerblade. However, all these exercises are for the lower body. There are few outdoor exercises for the upper body. Two choices are swimming and rowing, but lap pools and lakes are not readily available to most people. The arm-powered Land Rower will give able-bodied, as well as physically challenged, athletes a unique and well designed choice for upper body exercise.